Region-based information compaction as for digital images

ABSTRACT

A method and apparatus for preserving the dynamic range of a relatively high dynamic range information stream, illustratively a high resolution video signal, subjected to a relatively low dynamic range encoding and/or transport process(es). The invention subjects the relatively high dynamic range information stream to a segmentation and remapping process whereby each segment is remapped to the relatively low dynamic range appropriate to the encoding and/or transport process(es) utilized. An auxiliary information stream includes segment and associated remapping information such that the initial, relatively high dynamic range information stream may be recovered in a post-encoding (i.e. decoding) or post-transport (i.e., receiving) process.

[0001] This application is a continuation of U.S. patent applicationSer. No. 09/292,693, filed Apr. 15, 1999, which is a continuation inpart of U.S. patent application Ser. No. 09/050,304, filed on Mar. 30,1998 for Region-Based Information Compaction as for Digital Images,which are herein incorporated by reference in their entirety.

[0002] The invention relates to information processing systems ingeneral, and, more particularly, the invention relates to a method andapparatus for preserving a relatively high dynamic range of aninformation signal, such as a video information signal, processed via arelatively low dynamic range information processing system.

BACKGROUND OF THE DISCLOSURE

[0003] In some communications systems the data to be transmitted iscompressed so that the available bandwidth is used more efficiently. Forexample, the Moving Pictures Experts Group (MPEG) has promulgatedseveral standards relating to the compression of moving images anddigital data delivery systems. The first, known as MPEG-1 refers toISO/IEC standards 11172 and is incorporated herein by reference. Thesecond, known as MPEG-2, refers to ISO/IEC standards 13818 and isincorporated herein by reference. A compressed digital video system isdescribed in the Advanced Television Systems Committee (ATSC) digitaltelevision standard document A/53, and is incorporated herein byreference.

[0004] The above-referenced standards describe data processing andmanipulation techniques that are well suited to the compression anddelivery of video, audio and other information using fixed or variablelength digital communications systems. In particular, theabove-referenced standards, and other “MPEG-like” standards andtechniques, compress, illustratively, video information usingintra-frame coding techniques (such as run-length coding, Huffman codingand the like) and inter-frame coding techniques (such as forward andbackward predictive coding, motion compensation and the like).Specifically, in the case of video processing systems, MPEG andMPEG-like video processing systems are characterized by prediction-basedcompression encoding of video frames with or without intra- and/orinter-frame motion compensation encoding.

[0005] Within respect to still images (or single image frames), severalwell known standards are utilized to effect compression of imageinformation. For example, the Joint Photographic Experts Group (JPEG)has promulgated a several standard relating to the compression of stillimages, most notably the IS 10918-1 (ITU-T T.81) standard, which is thefirst of a multi-part set of standards for still image compression.

[0006] In the context of digital video processing and digital imageprocessing, information such as pixel intensity and pixel color depth ofa digital image is encoded as a binary integer between 0 and 2^(n−1).For example, film makers and television studios typically utilize videoinformation having 10-bit pixel intensity and pixel color depth, whichproduces luminance and chrominance values of between zero and 1023.While the 10-bit dynamic range of the video information may be preservedon film and in the studio, the above-referenced standards (andcommunication systems adapted to those standards) typically utilize adynamic range of only 8-bits. Thus, the quality of a film, video orother information source provided to an ultimate information consumer isdegraded by dynamic range constraints of the information encodingmethodologies and communication networks used to provide suchinformation to a consumer.

[0007] Therefore, it is seen to be desirable to provide a method andapparatus to preserve the dynamic range of film, video and other formsof relatively high dynamic range information that are encoded andtransported according to relatively low dynamic range techniques.Moreover, it is seen to be desirable to provide such dynamic rangepreservation while utilizing economies of scale inherent to theserelatively low dynamic range techniques, such as the above-referencedMPEG-like standards and techniques.

SUMMARY OF THE INVENTION

[0008] The invention comprises a method and apparatus for preserving thedynamic range of a relatively high dynamic range information stream,illustratively a high resolution video signal, subjected to a relativelylow dynamic range encoding and/or transport process(es). The inventionsubjects the relatively high dynamic range information stream to asegmentation and remapping process whereby each segment is remapped tothe relatively low dynamic range appropriate to the encoding and/ortransport process(es) utilized. An auxiliary information stream includessegment and associated remapping information such that the initial,relatively high dynamic range information stream may be recovered in apost-encoding (i.e. decoding) or post-transport (i.e., receiving)process.

[0009] Specifically, a method for encoding an information frameaccording to the invention comprises the steps of: dividing theinformation frame into a plurality of information regions, at least oneof the information regions comprising at least one information parameterhaving associated with it a plurality of intra-region values bounded byupper and lower value limits defining a dynamic range of the informationparameter; determining, for each of the at least one information region,a respective maximal value and a minimal value of the at least oneinformation parameter; remapping, for each of the at least oneinformation regions and according to the respective determined maximaland minimal values, the respective plurality of intra-region values ofthe at least one information parameter; and encoding each informationregion.

BRIEF DESCRIPTION OF THE DRAWING

[0010] The teachings of the present invention can be readily understoodby considering the following detailed description in conjunction withthe accompanying figures, in which:

[0011]FIG. 1 depicts a information distribution system;

[0012]FIG. 2 is a flow diagram of a combined information stream encodingmethod and decoding method;

[0013]FIG. 3A depicts an image that has been divided into a plurality ofregions using a pixel coordinate technique;

[0014]FIG. 3B depicts an image that has been divided into a plurality ofsingle macroblock regions defined by row and column;

[0015]FIG. 4A depicts a diagram illustrative of a non-linear encodingfunction;

[0016]FIG. 4B depicts a diagram illustrative of a non-linear decodingfunction associated with the encoding function of FIG. 4A; and

[0017]FIG. 5 depicts a high level function block diagram of an encodingand decoding method and apparatus.

[0018] To facilitate understanding, identical reference numerals havebeen used, where possible, to designate identical elements that arecommon to the figures.

DETAILED DESCRIPTION

[0019] After considering the following description, those skilled in theart will clearly realize that the teachings of the invention can bereadily utilized in any information processing system in whichrelatively high dynamic range information is subjected to relatively lowdynamic range processing (e.g., encoding), and subsequently reprocessed(e.g., decoded) to reproduce, ideally, the original high dynamic rangeinformation or an approximation thereto.

[0020] While the invention will primarily be discussed within thecontext of multiple or moving image processed (e.g., MPEG-like videoprocessing), it will be appreciated by those skilled in the art that theteachings of the present invention are readily applicable to single orstill image processing (e.g., JPEG-like image processing). Moregenerally, the teachings of the present invention are applicable to anyform of information comprising one or more information parameters havingassociated with them a relatively high dynamic range. The inventionprovides the capability to reduce that dynamic range for, e.g.,processing or transport, and subsequently restore that dynamic range.

[0021]FIG. 1 depicts an information distribution system 100 thatencodes, illustratively, a 10-bit dynamic range information stream usinga pre-processing function to produce a range enhancement informationstream, and an 8-bit encoding process, illustratively an MPEG-likeencoding process, to produce an 8-bit encoded information stream. The8-bit encoded information stream and the range enhancement informationstream are transported to, e.g., a receiver. At the receiver, the 8-bitencoded information stream is subjected to a decoding process,illustratively an MPEG-like decoding process, to produce an 8-bitdecoded information stream. A post-processing function utilizes therange enhancement information stream to enhance the dynamic range of the8-bit decoded information stream such that the original 10-bit dynamicrange is substantially restored.

[0022] The system 100 of FIG. 1 comprises an information coding section(10-30) suitable for use by, illustratively, an information providersuch as a television studio; an information distribution section (35),illustratively a communication channel such as a terrestrial broadcastchannel; and an information decoding section (40-60), suitable for useby, illustratively, an information consumer having an appropriatedecoding device.

[0023] The information coding section comprises a region map and scaleunit 10 that receives a relatively high dynamic range information signalS1, illustratively a 10-bit dynamic range video signal, from aninformation source such as a video source (not shown). The region mapand scale unit 10 divides each picture-representative,frame-representative or field-representative portion of the 10-bit videosignal S1 into a plurality of, respectively, sub-picture regions,sub-frame regions or sub-field regions. The operation of region map andscale unit 10 will be described in more detail below with respect toFIG. 2. Briefly, each of the plurality of regions are processed toidentify, illustratively, a maximum luminance level (Y_(max)) and aminimum luminance level (Y_(min)) utilized by pixels within theprocessed region. The luminance information within each region is thenscaled (i.e., remapped) from the original 10-bit dynamic range (i.e., 0to 1023) to an 8-bit dynamic range having upper and lower limitscorresponding to the identified minimum luminance level (Y_(min)) andmaximum luminance level (Y_(max)) of the respective region to produce,at an output, an 8-bit baseband video signal S3. The maximum and minimumvalues associated with each region, and information identifying theregion, are coupled to an output as a map region ID signal S4. In thecase of, e.g., a region not requiring dynamic range compaction, the mapregion ID signal may comprise an empty set.

[0024] An encoder 15, illustratively an MPEG-like video encoder (orJPEG-like image encoder), receives the remapped, 8-bit baseband video(or image) signal S3 from the region map and scale unit 10. The encoder15 encodes the 8-bit baseband video signal to produce a compressed videosignal S5, illustratively an MPEG-like video elementary stream.

[0025] An audio encoder 20, illustratively an MPEG-like audio encoder,receives a baseband audio signal S2 from an audio source (not shown).The baseband audio signal S2 is, typically, temporally related to thebaseband video signal S3. The audio encoder 20 encodes the basebandaudio signal to produce a compressed audio signal S16, illustratively anMPEG-like audio elementary stream. It must be noted that audio encoder20, and other audio functionality to be described later, is not strictlynecessary to the practice of the invention.

[0026] A service multiplexer 25 wraps the map region ID signal S4, theelementary stream S5 and the audio elementary stream S16 into respectivevariable-length or fixed length packet structures known as packetizedelementary streams. The packetized elementary streams (PES) are combinedto form a multiplexed PES S6. The PES structure provides, e.g.,functionality for identification and synchronization of decoding andpresentation of the video, audio and other information. A transportencoder 30 converts the PES packets of multiplexed PES S6 intofixed-length transport packets in a known manner to produce a transportstream S7.

[0027] It should be noted that the map region ID signal S4 may becommunicated to an end user (e.g., a decoder) via a plurality of meanswithin the context of, e.g., the various communications standards. Userprivate data tables and private data or message descriptorsincorporating the map region ID signal S4 may be placed in designatedlocations throughout messages as described in the MPEG and ATSCstandards. The use of such data, and other MPEG, ATSC, DVB and similarprivate, user or auxiliary data communication formats is contemplated bythe inventors. For example, since the map region ID signal S4 includesinformation corresponding to encoded region information within theelementary stream S5, in one embodiment of the invention the map regionID signal is included as private data within the multiplexed elementarystream S5.

[0028] The map region ID signal S4 may be communicated as an auxiliarydata stream, an MPEG-like data stream or a user private data or messagestream. Private data may comprise a data stream associated with aparticular packet identification (PID), private or user data insertedinto, e.g., a payload or header portion of another data stream (e.g., apacketized elementary stream including the elementary stream S5) orother portions of an information stream. In the case of a transportstream, the map region ID signal S4 is optionally incorporated into atransport stream private section.

[0029] In one embodiment of the invention, the transport encoderincludes, in a private data section of the transport stream beingformed, the dynamic range enhancement stream. In another embodiment ofthe invention, the transport encoder associated the encoded informationstream and the associated dynamic range enhancement stream withrespective packet identification (PID) values. In another embodiment ofthe invention, the transport encoder incorporates, into a packetizedstream, the encoded information stream. Additionally, the transportencoder includes, within a header portion of the packetized streamincorporating the encoded information stream, the associated dynamicrange enhancement stream.

[0030] The information distribution section comprises a communicationsnetwork 35, illustratively a terrestrial broadcast, fiber optic,telecommunications or other public or private data communicationsnetwork. The communications network receives the transport stream S7produced by the information coding section; modulates or encodes thetransport stream S7 to conform to the requirements of the communicationsnetwork (e.g., converting the MPEG transport stream S7 into anasynchronous transfer mode (ATM) format); transmits the modulated orencoded transport stream to, e.g., a receiver; and demodulates ordecodes the modulated or encoded transport stream to produce an outputtransport stream S8.

[0031] The information decoding section comprises a transport decoder 40that converts the received transport stream S8 into a multiplexed PESS9. The multiplexed PES S9 is demultiplexed by a service demultiplexer45 to produce a map region ID signal S14, a video elementary stream S12and an audio elementary stream S10 corresponding to, respectively, mapregion ID signal S4, elementary stream S5 and audio elementary streamS16.

[0032] The video elementary stream S12 is decoded in a known manner by avideo decoder 55 to produce, an 8-bit baseband video signal S13corresponding to the remapped 8-bit baseband video signal S3. The audioelementary stream S10 is decoded in a known manner by an audio decoder50 to produce a baseband audio output signal S11, corresponding to thebaseband audio signal S2, which is coupled to an audio processor (notshown) for further processing.

[0033] An inverse region map and scale unit 60 receives the 8-bitbaseband video signal S13 and the map region ID signal S14. The inverseregion map and scale unit 60 remaps the 8-bit baseband video signal S13,on a region by region basis, to produce a 10-bit video signal S15corresponding to the original 10-bit dynamic range video signal S1. Theproduced 10-bit video signal is coupled to a video processor (not shown)for further processing. The operation of inverse region map and scaleunit 60 will be described in more detail below with respect to FIG. 2.Briefly, the inverse region map and scale unit 60 retrieves, from themap region ID signal S14, the previously identified maximum luminancelevel (Y_(max)) and minimum luminance level (Y_(min)) associated witheach picture, frame or field region, and any identifying informationnecessary to associate the retrieved maximum and minimum values with aparticular region within the 8-bit baseband video signal S13. Theluminance information associated with each region is then scaled (i.e.,remapped) from the 8-bit dynamic range bounded by the identified minimumluminance level (Y_(min)) and maximum luminance level (Y_(max))associated with the region to the original 10-bit (i.e., 0-1023) dynamicrange to produce the 10-bit video signal S15. It will be appreciated bythose skilled in the art that other high dynamic range parametersassociated with an information signal (e.g., chrominance components,high dynamic range audio information and the like) may also beadvantageously processed using the apparatus and method of theinvention.

[0034] As previously noted, the map region ID signal S4 may becommunicated to an end user (e.g., a decoder) via a plurality of meanswithin the context of, e.g., the various communications standards. Thus,in one embodiment of the invention, the map region ID signal S4 isrecovered from a private data section of said transport stream. Inanother embodiment of the invention, the map region ID signal isassociated with a respective identification (PID) value and recoveredusing that value. In another embodiment of the invention, the encodedinformation stream is recovered from a packetized stream associated witha predefined packet identification (PID) value, while the map region IDsignal is retrieved form a header portion of the packetized streamassociated with the predefined packet identification (PID) value.

[0035]FIG. 2 is a flow diagram of a combined information stream encodingmethod and decoding method. The method 200 is entered at step 210 when arelatively high dynamic range information stream comprising a pluralityof logical information frames is received by, e.g., region map and scaleunit 10. The method 200 proceeds to step 215, where each logicalinformation frame of the received information stream is divided intoregions according to, illustratively, the criteria depicted in box 205which includes: fixed or variable coordinate regions based on picture,frame, field, slice macroblock, block and pixel location, related motionvector information and the like. In the case of a video informationstream, any exemplary region comprises a macroblock region size.

[0036] After dividing the logical information frames into regions (step215) the method 200 proceeds to step 220, where the maximum and minimumvalues of one or more parameters of interest are determined for eachregion. In the case of a video information signal, a parameter ofinterest may comprise a luminance parameter (Y) , color differenceparameter (U, V), motion vector and the like.

[0037] The method 200 then proceeds to step 225, where the parameters ofinterest in each pixel of each region are remapped to a parameter valuerange bounded by respective maximum and minimum parameter values. Thatis, if the parameter of interest of a pixel is a luminance parameter,all the luminance parameters within a particular region are remapped toa range determined by the maximum luminance value and the minimumluminance value within the particular region as previously determined instep 220.

[0038] The above described steps of regional division of logical frames,maximum and minimum parameter(s) determination and remapping comprisethe steps necessary to generate an information stream and an associateddynamic range enhancements stream. Specifically, dynamic rangedegradation visited upon the information stream due to a subsequent,relatively low dynamic range processing step (e.g., step 230 below), maybe largely corrected by a second, subsequent processing step (e.g.,steps 240-245 below). This concept is critical to the understanding ofthe invention.

[0039] After remapping all of the parameters of interest in one or moreregions (step 225), the method 200 proceeds to step 230, where theinformation within the region is encoded, to produce an encodedinformation stream. In the case of a video information stream, encodingmay comprise one of the MPEG-like encoding standards referenced above.The method 200 then proceeds to step 235, where the encoded informationstream, maximum and minimum data associated with each region of theencoded information stream, and information sufficient to associate eachregion with its respective maximum and minimum parameter(s) informationare transported to, e.g., a receiver. The method 200 then proceeds tostep 240, where the encoded information stream is decoded to produce adecoded information stream.

[0040] It is important to note that the dynamic range of the decodedinformation stream, specifically the dynamic range of the parameters ofinterest in the decoded information stream, will not exceed the dynamicrange of the encoding or processing methodology employed in, e.g., steps230-235. Thus, in the case of a ten bit dynamic range luminanceparameter of a video signal, and MPEG-like encoding and decodingmethodology which utilizes an eight bit dynamic range will produce, atthe decoder output, a video information stream having only an eight bitdynamic range luminance parameter.

[0041] After decoding the transported information stream (step 240), themethod 200 proceeds to step 245, where the eight bit dynamic rangedecoded information stream is remapped on a region by region basis usingthe respective maximum and minimum values associated with the parameteror parameters of interest in each region. The resulting relatively highdynamic range information stream is then utilized at step 250.

[0042] The portions of the above-described method 200 related toregional division and remapping will now be described in more detailbelow. In addition, the relationship of the invention to informationstreams in general, and video information streams in particular, willalso be described in more detail.

[0043] Information streams are typically segmented or framed accordingto a logical constraint. Each logical segment or frame comprises aplurality information elements, and each information element istypically associated with one or more parameters. In particular, videoinformation streams are typically segmented in terms of a picture, frameor field. The picture, frame or field comprises a plurality ofinformation elements known as picture elements (pixels). Each pixel isassociated with parameters such as luminance information and chrominanceinformation. In the case of MPEG-like systems, pixels are grouped intoblocks or macroblocks. Pixels, blocks and macroblocks may also haveassociated with them motion parameters and other parameters. Each of theparameters associated with a pixel, block or macroblock is accurate tothe extent that the dynamic range of the information defining theparameter is accurate. Moreover, preservation of the dynamic range ofsome parameters, such as pixel luminance, is more critical thanpreservation of the dynamic range of other parameters, such as blockmotion. As such, degradation of some parameters due to dynamic rangeconstraints may be acceptable, while other parameters should bepreserved with as high a fidelity as possible.

[0044] In the case of luminance parameters, in an image comprising verylight areas (i.e., high intensity values) and very dark areas (i.e., lowintensity values), the dynamic range of the luminance informationrepresenting the image may be fully utilized. That is, the value ofluminance parameters associated with pixels in the image may be between(in a 10-bit dynamic range representation) from zero (black) to 1023(white). Thus, if the dynamic range of the luminance informationrepresenting the image, illustratively a 10-bit studio image, exceedsthe dynamic range of an information processing operation used to processthe image, illustratively an 8-bit MPEG encoding operation, quantizationerrors will necessarily degrade the resulting processed image. However,by segmenting the image into smaller regions, the probability that thefull 10-bit dynamic range of the luminance information is utilized in aregion decreases.

[0045] Regions may be selected according to any intra-frame selectioncriteria. For example, in the case of a video information frame,appropriate criteria include scan lines, regions defined by pixelcoordinates, blocks, macroblocks, slices and the like. In general, thesmaller the region selected, the greater the probability of preservingthe full dynamic range of the information element parameter.

[0046]FIG. 3A depicts an image 300 that has been divided into aplurality of regions 301-307 using a pixel coordinate technique. In anembodiment of the invention utilizing region partitioning of an imageaccording to FIG. 3A, identifying indicia of region location comprisepixel coordinates defining, e.g., corners or edges of the regions.

[0047]FIG. 3B depicts an image 300 that has been divided into aplurality of single macroblock regions defined by row (R₁-R_(n)) andcolumn (C₁-C_(n)). Since the regions defined in FIG. 3B are much smallerthen the regions defined in FIG. 3A, there is a greater probability ofpreserving the dynamic range of the parameters of interest forming theimage. In an embodiment of the invention utilizing region partitioningof an image according to FIG. 3B, identifying indicia of region locationcomprise macroblock address, as defined by row (i.e., slice) number andcolumn number. A simpler method of region identification comprisesidentifying each region (i.e., macroblock) by a macroblock offset valuerepresenting the number of macroblocks from the start of a picture(i.e., the number of macroblocks from the top left, or first,macroblock).

[0048] A simple linear remapping of, e.g., pixel luminance orchrominance parameters from an original dynamic range to a targetdynamic range may be represented by equation 1, where TP=Target Pixel;OP=Original Pixel; TR=Target Range; and OR=original Range. In the caseof remapping a 10-bit pixel (such as used in a studio) to an 8-bit pixel(such as used in MPEG-like processing systems), equation 1 becomesequation 2. Similarly, in the case of remapping the 8-bit pixel back toa 10-bit pixel equation 1 becomes equation 3. It should be noted thatthe quantities or results within the floor function operators └ ┘ arerounded down to the nearest integer value.

TP=└OP*(TR/OR)+0.5┘  (eq. 1)

TP=└OP*(256/1024)+0.5┘  (eq. 2)

TP=└OP*(1024/256)+0.5┘  (eq. 3)

[0049] Using equation 2, an OP of 525 will result in a TP of 131. Usingequation 3, an OP of 131 will result in a TP of 524. It can be seen thatthe process of linear remapping from a 10-bit dynamic range to an 8-bitdynamic range and back to the 10-bit dynamic range results in a loss ofinformation due to quantization errors.

[0050] The above equations 1-3 mathematically illustrate thequantization error inherent in present remapping functions. By contrast,the below described remapping equations 4 and 5 are suitable for use in,respectively, the remapping equations suitable for use in, respectively,the region map and scale unit 10 and inverse region map and scale unit60 of FIG. 1.

[0051] In one embodiment of the invention a linear remapping function,such as the exemplary linear remapping function of equation 4, isutilized, where TP=Target Pixel; OP=Original Pixel; TR=Target Range;MAX=maximum parameter value and MIN=minimum parameter value. In the caseof a minimum of a 10-bit system having a regional minimum of 400 and aregional maximum of 600, equation 4 becomes equation 5.

TP=└(OP−MIN)*(TR/(MAX−MIN))+0.5┘  (eq. 4)

TP=└(OP−400)*(TR/(600-400))+0.5┘  (eq. 5)

[0052] Within the context of the invention, a function such as equation4 will be able to preserve the relatively high dynamic range of theoriginal pixel parameter as long as the difference between the maximumand minimum parameter values does not exceed a range defined by theratio of the original dynamic range and the target dynamic range. Thatis, in the case of a 10-bit original dynamic range and an 8-bit targetdynamic range where the ratio is 1023:255 (i.e., 4:1), the differencebetween the maximum and minimum values must not be greater than onefourth of the original dynamic range. Thus, a threshold level of dynamicrange for each region is established that determines if the full,original dynamic range of the parameter will be preserved by theinvention. Since, in equation 5, the difference between the maximum(600) and minimum (400) is less than one fourth of the 10-bit dynamicrange (256), full 10-bit dynamic range will be preserved.

[0053] It must be noted that equations 4 and 5 should not in any way beconstrued as limiting the scope of the invention. Rather, equations 4and 5 are presented as only one of a plurality of linear functionssuitable for use in the invention. The invention may also be practicedusing non-linear functions (such as gamma correction and compandingfunctions). Moreover, the invention may be practiced using a combinationof linear and non-linear functions to optimize data compaction. Thelinear and/or non-linear functions selected will vary depending on thetype of information stream being processed, the typical distribution ofparameters of interest within the information elements of that stream,the amount of dynamic range allowed for a given application, theprocessing constraints of the encoder and/or decoder operating on theinformation streams and other criteria.

[0054] To help ensure that the difference between the maximum andminimum values remains below the threshold level, it is desirable toreduce the size of the regions. However, a reduction in region sizenecessarily results in additional maximum and minimum information thatmust be identified and processed, though this overhead may not besignificant as will now be demonstrated.

[0055] The above-described method advantageously provides substantiallyfull dynamic range preservation of selected information elementparameters in an information frame. The cost, in terms of extra bitsnecessary to implement the invention, e.g., the overhead due to the useof minimum and maximum pixel values for each region of a picture, willnow be briefly discussed. Specifically, the additional number of bits tobe transported by, e.g., the communications network 35 of FIG. 1 will bediscussed.

[0056] Consider the case of preserving the 10-bit dynamic range of theluminance parameter of a video information stream processed according toan 8-bit dynamic range process. Assume that a small region size isselected, such as a 16×16 block of 8-bit pixels (monochrome). The 16×16block of 8-bit pixels is represented by 256*8 bits=2048 bits. Adding two10-bit values, a minimum and a maximum, to this block increases thenumber of bits by 20 to 2068 bits, or an increase of about 1%. In returnfor this, the pixel intensity resolution is never worse than 8 bits, andmay be as high as 10 bits, a factor of four improvement in the intensitydepth resolution.

[0057] Consider the case of a 10-bit digital video stream according tothe well known 4:4:4 format. In this case the luminance (Y) and colordifference (U, V) signals each have 10-bit dynamic range. Again,assuming that a small region size is selected, such as a 16×16 block of8-bit pixels. The 8-bit pixels are represented by 256*8*3 bits=6144bits. In this case also, adding six 10-bit values, a minimum and amaximum for each of the luminance (Y) and color difference (U, V)signals, to this block increases the number of bits by 60 to 6204 bits,or an increase of about 1%. In return for this, each of the luminance(Y) and color difference (U, V) signals are never worse than 8 bits, andmay be as high as 10 bits, a factor of four improvement in therespective intensity and color depth resolutions.

[0058] Returning now to the first case, if all the pixels were to berepresented by 10 bits, then the total number of bits would be256*10=2560 bits. In other words, full 10-bit representation wouldrequire 24% more bits than the regional coding described here. Thus, themethod provides a substantial improvement in dynamic range without acorrespondingly substantial increase in bit count. Moreover, byutilizing the method within the context of mass-produced encoder/decoderchipsets, such as the various implementations of the MPEG and MPEG-likecompression standards, JPEG and JPEG-like compression standards (andother known techniques) the method leverages the cost-savings ofexisting 8-bit chipsets to provide a 10-bit (or higher) effectivedynamic range.

[0059] The above-described embodiments of the invention achieve thedesired result using linear compaction methods. However, in someapplications it is desirable to process information using non-linearmethods. For example, analog video signals are non-linearly processed(i.e., “gamma corrected”) to compensate for non-linearity in, e.g.,picture tubes in television sets. Non-linear mapping methods accordingto the invention may be used to implement gamma correction and otherfunctions while preserving the dynamic range of the underlying signal.Moreover, linear and non-linear methods may be used together.

[0060] Another scenario appropriate for non-linear processing in themapping function occurs when there is a loss of accuracy because theoriginal range and the target range are too far apart, even with theabove-described intensity compaction methods. In this case, non-linearmapping is used to preserve the original pixel values (i.e., dynamicrange) over some part of the range. This situation is depicted belowwith respect to FIGS. 4A and 4B, where the information located within alower bit range (e.g., 0-131) is illustratively deemed to be moreimportant than the information located within an upper bit range (e.g.,132-1023).

[0061]FIG. 4A depicts a diagram 4 illustrative of a non-linear encodingfunction. The diagram comprises an original dynamic range 410A of 1024bits and a target dynamic range 420A of 255 bits. A signal 430A, 440Ahaving a 1024 bit dynamic range is remapped into the 255 bit dynamicrange space in two segments. The first segment 430A utilizes asubstantially linear transfer function, while the second segment 440Autilizes a compressed transfer function. That is, the range of 0-131 inthe original map is retained in the target map, while the range of 132to 1023 in the original map is compressed into the 132-255 range of thetarget map.

[0062]FIG. 4B depicts a diagram illustrative of a non-linear decodingfunction associated with the encoding function of FIG. 4A. Thus, toretrieve, at a decoder, the information signal encoded according to aremapping function having the transfer function depicted in FIG. 4A, thedecoder implements a remapping function having the transfer functiondepicted in FIG. 4B.

[0063]FIG. 5 depicts a high level function block diagram of an encodingand decoding method and apparatus according to the invention.Specifically, the encoding and decoding method and process comprises afunction mapper 530, which is responsive to an information stream S1received from, illustratively, a pixel source 510. The function mapperremaps the information stream S1 according to various function criteriaf_(c) provided by a function criteria source 520 to produce a remappedinformation stream S3 and an associated map information stream S4.

[0064] The remapped information stream S3 is coupled to an encoder 540that encodes the remapped information stream S3 to produce an encodedinformation stream S5. The encoded information stream S5 and the mapinformation stream S4 are transported to, respectively, a decoder 550and an inverse function mapper 560.

[0065] The decoder 550 decodes the transported and encoded informationstream to retrieve an information stream substantially corresponding tothe initial remapped information stream.

[0066] The inverse function mapper 560 performs, in accordance with thetransported map information stream S4, an inverse function mappingoperation on the retrieved stream to produce an information streamsubstantially corresponding to the original information stream. It mustbe noted that the information stream produced by the inverse functionmapper 560 may advantageously include linear and/or non-linearmodifications in furtherance of the specific application (e.g., gammacorrection and the like).

[0067] It should be noted that the function mapper 530 and inversefunction mapper 560 may be operated in substantially the same manner asthe region map and scale unit 10 and inverse region map and scale unit60 depicted in FIG. 1.

[0068] In one embodiment of the invention, the remapping functionperformed by, e.g., the function mapper 530 or region map and scale unit10 performs a remapping function according to an arbitrary function. Anarbitrary function remapping of, e.g., pixel luminance or chrominanceparameters from an original dynamic range to a target dynamic range maybe represented by equation 6, where TP=Target Pixel; OP=Original Pixel;TR=Target Range; OR=original Range; MAX=maximum value; MIN=minimumvalue; and F=the arbitrary function.

TP=F(OP,MAX,MIN,TR)  (eq. 6)

[0069] It is important to note that the function F may take a number offorms and be implemented in a number of ways. For example, the functionF may implement: 1) a simple linear function such as described abovewith respect to FIGS. 1-2; 2) a gamma correction function that variesinput video intensity levels such that they correspond to intensityresponse levels of a display device; 3) an arbitrary polynomial; or 4) atabulated function (i.e., a function purely described in terms of alookup table, where each input bit addresses a table to retrieve thecontents stored therein.

[0070] In the case of remapping using a fixed gamma correction function,a function of the following form may be implemented:

TP=└F[(OP−MIN)^(γ) *TR/(MAX−MIN)^(γ)]+0.5┘  (eq. 7)

[0071] In the case of remapping using a polynomial segment,illustratively a parabola (X²+X), a function of the following form maybe implemented, assuming that the polynomial segment is never be lessthan 0 nor greater than the target range:

TP=└[(OP−MIN)²+(OP−MIN)* TR/[(MAX−MIN)²+(MAX−MIN)]+0.51┘  (eq. 8)

[0072] In the case of remapping using a tabulated function, the tablecomprises an indexable array of values, where the index values are theoriginal range and the values in the table are included in the targetrange. This allows any arbitrary mapping between the two ranges. Unless,like gamma correction, that mapping is one-way only (i.e., the remappingis not intended to be “unmapped”), then there an inverse table at thedecoder 550 or inverse map and scale unit 60 will restore the originalinformation values.

[0073] It should be noted that the terms dynamic range enhancementstream and map region identification stream are used in substantiallythe same manner to describe information streams carrying auxiliary orother data suitable for use in recovering at least a portion of thedynamic range of an information stream processed according to theinvention.

[0074] Although various embodiments that incorporate the teachings ofthe present invention have been shown and described in detail herein,those skilled in the art can readily devise many other variedembodiments that still incorporate these teachings.

What is claimed is:
 1. A method for encoding an information frame,comprising the steps of: dividing said information frame into aplurality of information regions, at least one of said informationregions comprising at least one information parameter having associatedwith it a plurality of intra-region values bounded by upper and lowervalue limits defining a dynamic range of said information parameter;determining, for each of said at least one information region, arespective maximal value and a minimal value of said at least oneinformation parameter; remapping, for each of said at least oneinformation regions and according to a single manipulation of therespective determined maximal and minimal values, said respectiveplurality of intra-region values of said at least one informationparameter; and encoding each information region.
 2. The encoding methodof claim 1, wherein said steps of encoding and determining produce,respectively, an encoded information stream and an associated dynamicrange enhancement stream, said encoding method further comprising thestep of: transport encoding said encoded information stream and saidassociated dynamic range enhancement stream to form a transport streamfor subsequent transmission.
 3. The encoding method of claim 2, whereinsaid step of transport encoding comprises the step of: including, in aprivate data section of said transport stream, said dynamic rangeenhancement stream.
 4. The encoding method of claim 2, wherein said stepof transport encoding comprises the step of: associating said encodedinformation stream and said associated dynamic range enhancement streamwith respective packet identification (PID) values.
 5. The encodingmethod of claim 2, wherein said step of transport encoding comprises thesteps of: incorporating, into a packetized stream, said encodedinformation stream; and including, within a header portion of saidpacketized stream, said associated dynamic range enhancement stream. 6.The encoding method of claim 2, further comprising the steps of:transport decoding said transport stream to recover said encodedinformation stream and said associated dynamic range enhancement stream;decoding said recovered encoded information stream to recover saidinformation regions; and inverse remapping, according to said respectivemaximal and minimal values, each of said at least one informationparameters of said at least one information regions having associatedwith it a plurality of respective remapped intra-region values.
 7. Theencoding method of claim 1, wherein: said information frame comprises animage frame and said at least one information parameter comprises atleast one of a luminance parameter and a chrominance parameter; and saidsteps of encoding and determining produce, respectively, an encodedimage stream and an associated dynamic range enhancement stream.
 8. Theencoding method of claim 7, wherein said encoding step comprisescompression encoding, using one of an JPEG-like compression encoder andan MPEG-like compression encoder, said information regions forming saidinformation frame.
 9. The encoding method of claim 8, further comprisingthe step of: transport encoding said encoded information stream and saidassociated dynamic range enhancement stream to form a transport streamfor subsequent transmission.
 10. The encoding method of claim 9, furthercomprising the steps of: transport decoding said transport stream torecover said encoded information stream and said associated dynamicrange enhancement stream; compression decoding said received encodedinformation stream to recover said remapped information regions; andinverse remapping, according to said respective maximal and minimalvalues, each of said at least one information parameters of said atleast one information regions having associated with it a plurality ofrespective remapped intra-region values.
 11. The encoding method ofclaim 8, wherein each information region is defined with respect to oneof a picture, frame, field, slice, macroblock, block, pixel location,and motion vector.
 12. The encoding method of claim 7, wherein said stepof remapping is performed in accordance with the following linearequation: TP=└OP*(TR/OR)+0.5┘where: TP=Target Pixel; OP=Original Pixel;TR=Target Range; and OR=original Range.
 13. The encoding method of claim7, wherein said step of remapping is performed in accordance with anon-linear function comprising one of a gamma correction function and acompanding function.
 14. The encoding method of claim 1, wherein saidstep of remapping is performed in accordance one of a linear remappingfunction and a non-linear remapping function.
 15. The encoding method ofclaim 1, wherein said steps of defining, determining, remapping andencoding are repeated for each of a plurality of information frames. 16.The encoding method of claim 15, wherein: said plurality of informationframes comprise image frames, said at least one information parametercomprises at least one of a luminance parameter and a chrominanceparameter; and said steps of encoding and determining produce,respectively, an encoded image stream and an associated dynamic rangeenhancement stream.
 17. The encoding method of claim 15, wherein saidencoding step comprises compression encoding, using an MPEG-likecompression encoder, each information frame of said information stream.18. The encoding method of claim 17, further comprising the step oftransport encoding said encoded information stream and said associateddynamic range enhancement stream to form a transport stream forsubsequent transmission.
 19. The encoding method of claim 18, furthercomprising the steps of: transport decoding said transport stream torecover said encoded information stream and said associated dynamicrange enhancement stream; compression decoding said received encodedinformation stream to recover said remapped information regions; andinverse remapping, according to said respective maximal and minimalvalues, each of said at least one information parameters of said atleast one information regions having associated with it a plurality ofrespective remapped intra-region values.
 20. The encoding method ofclaim 16, wherein each information region is defined with respect to oneof a picture, frame, field, slice, macroblock, block, pixel location,and motion vector.
 21. The encoding method of claim 16, wherein saidstep of remapping is performed in accordance with the following linearequation: TP=└OP*(TR/OR)+0.5┘where: TP=Target Pixel; OP=Original Pixel;TR=Target Range; and OR=original Range.
 22. The encoding method of claim16, wherein said step of remapping is performed in accordance with anon-linear function comprising one of a gamma correction function and acompanding function.
 23. A method for decoding an encoded informationframe represented by a plurality of encoded information regions withinan encoded information stream, where at least one of said plurality ofencoded information regions comprises at least one information parameterhaving associated with it a plurality of remapped intra-region values,said method comprising the steps of: decoding each of said plurality ofencoded information regions to form a corresponding plurality of decodedinformation regions, said decoded information regions representing adecoded information frame; extracting, from a dynamic range enhancementstream associated with said encoded information stream, respectivemaximal and minimal values for each of said at least one informationparameter having associated with it a plurality of remapped intra-regionvalues; and inverse remapping, according to a single manipulation ofsaid respective maximal and minimal values, each of said at least oneinformation parameter of said at least one information regions havingassociated with it a respective plurality of remapped intra-regionvalues.
 24. The decoding method of claim 23, wherein said encodedinformation stream and said dynamic range enhancement stream associatedwith said encoded information stream comprises respective portions of atransport stream, said decoding method further comprising the step of:demultiplexing said transport stream to recover said encoded informationstream and said dynamic range enhancement stream.
 25. The decodingmethod of claim 24, wherein said step of demultiplexing comprises thestep of: retrieving, from a private data section of said transportstream, said dynamic range enhancement stream.
 26. The decoding methodof claim 24, wherein said step of demultiplexing comprises the step of:retrieving, according to respective packet identification (PID) values,said encoded information stream and said associated dynamic rangeenhancement stream.
 27. The decoding method of claim 24, wherein saidstep of demultiplexing comprises the step of: retrieving, from apacketized stream associated with a predefined packet identification(PID) value, said encoded information stream, said encoded informationstream; and retrieving, from a header portion of said packetized streamassociated with a predefined packet identification (PID) value, saidassociated dynamic range enhancement stream.
 28. The decoding method ofclaim 25, wherein said decoded information frame comprises an imageframe and said at least one information parameter comprises at least oneof a luminance parameter and a chrominance parameter.
 29. The decodingmethod of claim 28, wherein said decoding step comprises compressiondecoding, using an MPEG-like compression decoder, said encodedinformation frame of said information stream.
 30. The decoding method ofclaim 28, wherein said step of inverse remapping is performed inaccordance with the following linear equation: TP=└OP*(TR/OR)+0.5┘where:TP=Target Pixel; OP=Original Pixel; TR=Target Range; and OR=originalRange.
 31. The decoding method of claim 28, wherein said step of inverseremapping is performed in accordance with a non-linear functioncomprising one of a gamma correction function and a companding function.32. The decoding method of claim 28, wherein each information region isdefined with respect to one of a picture, frame, field, slice,macroblock, block, pixel location, and motion vector.
 33. The decodingmethod of claim 23, wherein said steps of decoding, extracting andinverse remapping are repeated for each of a plurality of informationframes within said encoded information stream and said dynamic rangeenhancement stream associated with said encoded information stream. 34.The decoding method of claim 33, wherein: said plurality of informationframes comprise image frames, said at least one information parametercomprises at least one of a luminance parameter and a chrominanceparameter.
 35. The decoding method of claim 34, wherein said decodingstep comprises compression decoding, using an MPEG-like compressiondecoder, said encoded information frame of said information stream. 36.The decoding method of claim 34, wherein said step of inverse remappingis performed in accordance with the following linear equation:TP=└OP*(TR/OR)+0.5┘where: TP=Target Pixel; OP=Original Pixel; TR=TargetRange; and OR=original Range.
 37. The decoding method of claim 34,wherein said step of inverse remapping is performed in accordance with anon-linear function comprising one of a gamma correction function and acompanding function.
 38. The decoding method of claim 34, wherein eachinformation region is defined with respect to one of a picture, frame,field, slice, macroblock, block, pixel location, and motion vector. 39.In an information processing system including an information processortending to reduce the dynamic range of a relatively high dynamic rangeinformation element within an information stream processed therein, amethod for substantially preserving the dynamic range of said relativelyhigh dynamic range information element comprising the steps of:segmenting said information stream into a plurality of informationregions; determining the value of each occurrence of said relativelyhigh dynamic range information element within each of said respectiveinformation regions; generating indicia of a range of said determinedvalues within each of said respective information regions; remapping, inaccordance with the respective generated statistical indicia and thedynamic range of said dynamic range reducing process, the value of eachoccurrence of said relatively high dynamic range information elementwithin each of said respective information regions to produce a remappedinformation stream; and processing, according to said dynamic rangereducing process, said remapped information stream to produce a dynamicrange reduced information stream comprising a plurality of informationregions including respective dynamic range reduced information elements.40. The method of claim 39, further comprising the step of: inverseremapping, in accordance with respective generated indicia, the value ofeach occurrence of said dynamic range reduced information elementswithin each of said information regions of said dynamic range reducedinformation stream, to produce an dynamic range restored informationstream.
 41. Apparatus for processing an information stream comprising aplurality of information frames, said apparatus comprising: a regionalmap and scale unit, coupled to receive said information stream, forsegmenting a received information frame into one or more informationregions, and for remapping one or more relatively high dynamic rangeinformation parameters associated with each information region accordingto respective intra-region information parameter maxima and minima toproduce a remapped information stream and an associated map regionidentification stream, said one or more remapped information parametershaving a relatively low dynamic range; and a compression encoder,coupled to said regional map and scale unit, for compression encodingsaid remapped information stream to produce a compression encodedinformation stream, wherein said regional map and scale unit imparts atransfer characteristic to said remapped information stream comprisingat least one of a gamma correction characteristic, a compandingcharacteristic, a redistribution characteristic, a linearcharacteristic, an arbitrary polynomial characteristic and apre-determined function characteristic.
 42. Apparatus for processing aninformation stream comprising a plurality of information frames, saidapparatus comprising: a regional map and scale unit, coupled to receivesaid information stream, for segmenting a received information frameinto one or more information regions, and for remapping one or morerelatively high dynamic range information parameters associated witheach information region according to respective intra-region informationparameter maxima and minima to produce a remapped information stream andan associated map region identification stream, said one or moreremapped information parameters having a relatively low dynamic range;and an compression encoder, coupled to said regional map and scale unit,for compression encoding said remapped information stream to produce acompression encoded information stream, wherein each information regionis defined with respect to one of a picture, frame, field, slice,macroblock, block, pixel location, and motion vector.
 43. An apparatusfor decoding an encoded information frame represented by a plurality ofencoded information regions within an encoded information stream, whereat least one of said plurality of encoded information regions comprisesat least one information parameter having associated with it a pluralityof remapped intra-region values, said apparatus comprising: a decoder,for decoding each of said plurality of encoded information regions toform a corresponding plurality of decoded information regions, saiddecoded information regions representing a decoded information frame;and an inverse map and scale unit, for extracting, from a dynamic rangeenhancement stream associated with said encoded information stream,respective maximal and minimal values for each of said at least oneinformation parameter having associated with it a plurality of remappedintra-region values; said and inverse map and scale unit inverseremapping, according to a single manipulation of said respective maximaland minimal values, each of said at least one information parameter ofsaid at least one information regions having associated with it arespective plurality of remapped intra-region values.
 44. The apparatusof claim 43, wherein said encoded information stream and said dynamicrange enhancement stream associated with said encoded information streamcomprises respective portions of a transport stream, said apparatusfurther comprising: a transport decoder and demultiplexer, forprocessing said transport stream to recover said encoded informationstream and said dynamic range enhancement stream.
 45. The apparatus ofclaim 44, wherein said transport decoder and demultiplexer retrieves,from a private data section of said transport stream, said dynamic rangeenhancement stream.
 46. The apparatus of claim 44, wherein saidtransport decoder and demultiplexer retrieves, according to respectivepacket identification (PID) values, said encoded information stream andsaid associated dynamic range enhancement stream.
 47. The apparatus ofclaim 44, wherein: said transport decoder and demultiplexer retrieves,from a packetized stream associated with a predefined packetidentification (PID) value, said encoded information stream, saidencoded information stream; and said transport decoder and demultiplexerretrieves, from a header portion of said packetized stream associatedwith a predefined packet identification (PID) value, said associateddynamic range enhancement stream.
 48. The apparatus of claim 43,wherein: said decoded information frame comprises an image frame andsaid at least one information parameter comprises at least one of aluminance parameter and a chrominance parameter; and said compressiondecoder comprises an MPEG-like compression decoder.
 49. The apparatus ofclaim 48, wherein: said inverse map and scale unit performs said inverseremapping function in accordance with the following linear equation:TP=└OP*(TR/OR)+0.5┘ where: TP=Target Pixel; OP=Original Pixel; TR=TargetRange; and OR=original Range.
 50. The apparatus of claim 48, wherein:said inverse map and scale unit performs said inverse remapping functionin accordance with a non-linear function comprising one of a gammacorrection function and a companding function.
 51. The apparatus ofclaim 48, wherein each information region is defined with respect to oneof a picture, frame, field, slice, macroblock, block, pixel location,and motion vector.
 52. The apparatus of claim 43, wherein: said encodedinformation stream and said dynamic range enhancement stream associatedwith said encoded information stream represent a plurality of encodedinformation frames; and said apparatus processes each of said pluralityof encoded information frames to produce a corresponding plurality ofdecoded information frames.
 53. The apparatus of claim 52, wherein saidplurality of decoded information frames comprise image frames and saidat least one information parameter comprises at least one of a luminanceparameter and a chrominance parameter; and said compression decodercomprises an MPEG-like compression decoder.
 54. The apparatus of claim53, wherein: said inverse map and scale unit performs said inverseremapping function in accordance with the following linear equation:TP=└OP*(TR/OR)+0.5┘ where: TP=Target Pixel; OP=Original Pixel; TR=TargetRange; and OR=original Range.
 55. The apparatus of claim 53, wherein:said inverse map and scale unit performs said inverse remapping functionin accordance with a non-linear function comprising one of a gammacorrection function and a companding function.
 56. The apparatus ofclaim 53, wherein each information region is defined with respect to oneof a picture, frame, field, slice, macroblock, block, pixel location,and motion vector.